1. Field of the Invention
The present invention relates to an IP telephone apparatus that can be applied to an IP telephone system utilizing ENUM (tElephone NUmber Mapping) technology.
2. Description of Related Art
Recently, telecommunications providers have built VoIP (Voice over Internet Protocol) network on the Internet and provided services that connect IP telephone apparatuses owned by subscribers on these VoIP networks. In addition, low-cost communication services have been provided wherein PSTN (Public Switched Telephone Network) and VoIP networks that are provided by telecommunications providers are connected, thereby establishing a connection via such a VoIP network when a call is placed from an IP telephone apparatus to an ordinary telephone apparatus at a remote place. Furthermore, besides services provided by telecommunications providers via VoIP networks using a 050 number system, multimedia communication services including voice communication have been provided by service providers by building their own independent communication networks. When subscribing to these service providers in order to get such communication services, specific numbers (not limited to numerals) that specify subscribers on their independent communication networks are assigned, as is the case with regular telephone numbers.
As described above, current IP telephone apparatuses may be configured to have regular telephone numbers that are used when using PSTN services, 050 telephone numbers that are used when using IP telephone services provided by telecommunications providers on the Internet (VoIP network), and specific numbers that are used when using voice communication services provided by service providers on the Internet based on non-050 number systems (independent communication network).
Users are able to select and dial, using a specific number that enables the lowest call rate, by identifying in advance service types that the call destination is able to use and specific numbers needed to receive those individual communication services.
In addition, telephone apparatuses equipped with an LCR (Lowest Cost Routing) function are also known (Refer to Related Art 1, for example). Such telephone apparatuses with the LCR function write in, in a selection table therein, information needed to select, from the telephone numbers of the call destination, the lowest cost telephone line at the time of call and selects the lowest cost telephone line by referring to the selection table based upon the specified telephone number.
[Related Art 1] Japanese Patent Laid-Open Publication 8-130594
As described above, when one IP telephone apparatus has a plurality of specific numbers, the lowest-cost communication service combination is determined by a particular combination of communication services available to the caller and communication services available to the call destination. However, it is difficult for the caller to not only memorize communication services available to the source IP telephone apparatus but also identify communication services available to the destination IP telephone apparatus in order to establish a connection with the destination IP telephone apparatus in the most economical way. In addition, telephone apparatuses with the LCR function are not configured to select the lowest-cost line by identifying communication services available to both caller and call destination.